The chemical, food and beverage processing industries use a variety of process, transportation and storage vessels which must be periodically cleaned. Typically, such vessels or tanks are cleaned by a spraying apparatus which uses the cleaning fluid to be sprayed within the tank to drive the spray assembly in a predetermined pattern. Typically such devices are designed to rotate about two perpendicular axis at the same time. That is, the spray nozzle rotates about a first axis and the portion of the device that the spray nozzle is mounted is simultaneously rotated about a second axis which is generally perpendicular to the first axis. This provides a spray cleaning pattern which covers the interior of the vessel in a quick and efficient manner. An example of such a prior art device is illustrated by U S. Pat. No. 3,637,137. More particularly, these devices typically comprise a stationary inlet housing having a first generally vertical axis, a Tee-housing that is rotatably mounted to the inlet housing so as to rotate about a first vertical axis and a spray nozzle assembly secured to the Tee-housing which is designed to rotate about a second axis which is substantially perpendicular to the vertical axis. Positive gearing means are used to drive the Tee-housing and nozzle assembly in a predetermined pattern. In order to provide an appropriate fluid passageway between the stationary inlet housing and Tee-housing, a plurality of spaced discharge openings are placed about the circumference of the inlet stem. The Tee-housing comprises a generally cylindrical body which forms a receiving chamber with the inlet stem for receiving fluid from the discharge opening of the inlet stem, and a nose section for directing fluid into the nozzle assembly. The nose section is positioned adjacent the discharge openings. A problem encountered with such device is that as the Tee-housing rotates about the inlet stem, the discharge openings in the inlet stem communicate in a periodic fashion with the nose section of the Tee-housing. This results in pulsating fluid pressure in the Tee-housing. This affects the fluid flow within the device and ultimately its cleaning efficiency. An additional problem with such prior art devices is the difficulty in providing a smooth and uninterrupted flow pattern due to the three part assembly necessary for the dual rotational movement.
Applicant has invented an improved tank cleaning apparatus which minimizes or eliminates the pulsating pressure effect and also provides improved fluid flow pattern within the device while still providing a controlled predetermined spray pattern.